The present invention relates generally to the manufacture of bicycles having a frame of the well known "diamond" configuration. These are made of light weight tubing and have wheel bearing brackets or drop outs at the rear and front forks. At the rear wheel, the drop outs connect the rear fork assembly to the rear axle. At the front wheel, they connect the front fork assembly to the front axle.
In high quality bicycles there is an emphasis on light weight to improve pedaling response, and on frame rigidity to improve pedaling ease and avoid inefficient deflection of the frame at each pedal stroke.
The drop outs are critically important components because they tie the frame together at the ends which directly receive road shocks. To provide the strength and the light weight required, many have been manufactured by conventional hot forging techniques which require costly tools and dies, lavish amounts of expensive mechanical and thermal energy, and substantial investment in heavy machinery and highly skilled labor. Grinding and chrome-plating opposite faces have added further to the cost.
More recently, attempts have been made to reduce this cost by laminating die-cut stainless steel face plates on opposite sides of a base plate punchment, using an electric press-welding technique, as described in U.S. Pat. No. 4,524,989 issued June 25, 1985, to Norman L. Centeny on "Laminated Reinforced Fork End Fitment Connector For A Bicycle And Process For Manufacturing Same".
In spite of the cost savings in such new manufacturing methods, there is another area of substantial expense which has been completely overlooked: the necessity of building, and stocking, a special rear wheel drop out bracket for each and every size of bicycle frame.
In the rear fork assembly of the above mentioned diamond configuration frame, the drop out brackets have pairs of forwardly and upwardly extending, angularly offset extension lugs which fit telescopically within and are welded or brazed to the ends of the seat stay and chain stay tubes.
A full line of bicycles between the 25-inch and 19-inch frames may require as many as seven different drop outs, each with their above-mentioned extension lugs angularly offset both laterally and longitudinally to match the angles of the seat stay and chain stay tubes.
To build and maintain the tooling and production machinery for seven different size drop outs, and to keep all seven sizes in stock, are substantial and unnecessary expenses which are eliminated by the present invention.